Computational modeling and experiment validation of a microchannel cross-flow heat exchanger

Abstract

Microchannel Cross-Flow Heat Exchanger (MCFHE) is one of the potential candidates to be employed in various energy recovery. Compared to microchannel counter-flow heat exchanger, little research has been devoted to simulating the heat transfer process inside a MCFHE. Given the complex temperature distributions associated with cross-flow heat exchangers, the conventional “unit cell” approach for a pair of fluid channels becomes invalid. In this study, a new methodology is developed to resolve the modeling challenges associated with a 2-pass MCFHE. Specifically, the MCFHE is divided into 10 zones to minimize mesh size associated with each fluid channel, which leads to a computationally efficient and segregated CFD model. The CFD model provides detailed temperature distributions within both fluid channels, and the resulted outlet temperatures match closely with the experimental data. In addition, the Nusselt numbers in the air and oil channels agree well with classical developing flow correlations. Using the ε−NTU method, it provides an initial guess for the mid-pass oil temperature that is needed to initiate the CFD simulations for the first pass including Zone 1–5. Furthermore, the resulted analytical results based on the iterative ε−NTU method match closely with the CFD simulations.